The present invention provides for very fast detection of gaze direction using retro-reflected light from the ocular fundus that is cost-efficient, small, and portable. These eye trackers are useful in many areas of science and technology, including but not limited to remote control, space, defense, medical and psycho-physiological applications, to identify for example subtle neurologic deficits that occur with cerebellar or vestibular disorders, Parkinson's disease, strokes, traumatic brain injury, possible concussions during sports matches, some forms of reading disability, or simply fatigue or inebriation. In ophthalmology, with two such devices operating simultaneously, the variability of relative eye alignment over time can be measured, without requiring individual calibration, and without requiring fixation on a specified target, ideal for use with small children. Such instruments have widespread application as noninvasive screening devices in infants and young children or patients of any age for defects of binocular function such as strabismus and amblyopia.

An ultrafast system for detecting incidence of a single photon is disclosed which includes a single photon avalanche detector having an inherent bandgap, a source of probe light configured to apply an incident beam onto the single photon avalanche detector, wherein the probe light is configured to apply energy less than the bandgap, and a probe beam detector, configured to receive a reflected probe beam from the single photon avalanche detector, wherein the probe beam detector is adapted to generate a signal signifying: i) incidence of a single photon from a control beam onto the single photon avalanche detector.

A well-logging tool may include a sonde housing, and a radiation generator carried by the sonde housing. The radiation generator may include a generator housing, a target carried by the generator housing, a charged particle source carried by the generator housing to direct charged particles at the target, and at least one voltage source coupled to the charged particle source. The at least one voltage source may include a voltage ladder comprising a plurality of voltage multiplication stages coupled in a bi-polar configuration, and at least one loading coil coupled at at least one intermediate position along the voltage ladder. The well-logging tool may further include at least one radiation detector carried by the sonde housing.

A well-logging tool may include a sonde housing, and a radiation generator carried by the sonde housing. The radiation generator may include a generator housing, a target carried by the generator housing, a charged particle source carried by the generator housing to direct charged particles at the target, and at least one voltage source coupled to the charged particle source. The at least one voltage source may include a voltage ladder comprising a plurality of voltage multiplication stages coupled in a bi-polar configuration, and at least one loading coil coupled at at least one intermediate position along the voltage ladder. The well-logging tool may further include at least one radiation detector carried by the sonde housing.

An electron multiplier includes an insulating substrate which includes an electrical wiring pattern and in which a through-hole is formed, an MCP arranged on one side of the through-hole of the insulating substrate and electrically connected to the electrical wiring pattern, a shield plate arranged in one side of the MCP and electrically connected to the MCP, an anode arranged on the other side of the through-hole and electrically connected to the electrical wiring pattern, and a signal readout terminal fixed to the insulating substrate for reading a signal from the anode. The shield plate is formed to include the MCP when viewed in a thickness direction. A through-hole exposing at least a portion of the MCP is formed in the shield plate. The insulating substrate, the MCP, the shield plate and the anode are fixed to each other to be integral.

An electron multiplier includes an insulating substrate which includes an electrical wiring pattern and in which a through-hole is formed, an MCP arranged on one side of the through-hole of the insulating substrate and electrically connected to the electrical wiring pattern, a shield plate arranged in one side of the MCP and electrically connected to the MCP, an anode arranged on the other side of the through-hole and electrically connected to the electrical wiring pattern, and a signal readout terminal fixed to the insulating substrate for reading a signal from the anode. The shield plate is formed to include the MCP when viewed in a thickness direction. A through-hole exposing at least a portion of the MCP is formed in the shield plate. The insulating substrate, the MCP, the shield plate and the anode are fixed to each other to be integral.

An electron tube used by being attached to an external device, including a housing having a light incident window including a light incident surface and allowing light from the external device to be incident thereon through the light incident surface, a photoelectric conversion portion disposed inside the housing to face the light incident window, and configured to emit electrons in response to the light incident from the light incident window, an electron multiplier portion disposed inside the housing and configured to multiply electrons emitted from the photoelectric conversion portion, and a positioning member formed separately from the light incident window and fixed to the light incident surface, the positioning member having a light passing portion passing the light from the external device toward the light incident surface, in which the positioning member has a reference portion serving as a reference for mechanical positioning with respect to the external device.

An electron tube used by being attached to an external device, including a housing having a light incident window including a light incident surface and allowing light from the external device to be incident thereon through the light incident surface, a photoelectric conversion portion disposed inside the housing to face the light incident window, and configured to emit electrons in response to the light incident from the light incident window, an electron multiplier portion disposed inside the housing and configured to multiply electrons emitted from the photoelectric conversion portion, and a positioning member formed separately from the light incident window and fixed to the light incident surface, the positioning member having a light passing portion passing the light from the external device toward the light incident surface, in which the positioning member has a reference portion serving as a reference for mechanical positioning with respect to the external device.

An arithmetic device that calculates a gain of a photomultiplier tube includes: an acquisition unit that acquires a digital signal based on a dark pulse output from the photomultiplier tube placed in a dark state; and a calculation unit that calculates a total number of electrons in the dark pulse based on the digital signal and calculates the gain of the photomultiplier tube based on the total number of electrons.